What is the difference between a direct injection engine and a regular engine?

FSI, "direct-injection engine", "direct-injection gasoline engine". It is a leading technology unique to Audi, which maximizes and optimizes the intake air mixing efficiency, so that efficient fuel saving and high power output are no longer contradictory. The Audi FSI increases the torque and output of spark-ignition engines while increasing economy by 15 percent and laying the foundation for lower emissions. Compared to conventional ignition engines, FSI injects fuel directly into the combustion chamber, eliminating the need for a throttle and reducing heat loss from the engine, thus increasing output and reducing fuel consumption. Specifically: FSI is the letter abbreviation of Fuel Stratified Injection, which means Fuel Stratified Injection technology in Chinese, and it represents a development direction for future engines. Traditional gasoline engines use a computer to collect cam positions and all relevant engine conditions to control the injector nozzles to inject gasoline into the intake manifold. The gasoline is mixed in the manifold and then burned in the cylinders. The optimal mixing ratio of air and gasoline is 14.7/1 (also called the theoretical air-fuel ratio), the traditional engine because the gasoline and air are mixed in the intake manifold, so they can only be evenly mixed together, so it must reach the theoretical air-fuel ratio in order to achieve better power and economy, but due to the injector nozzle from the combustion chamber there is a certain distance, the mixing of gasoline with the air by the intake airflow and valve switching However, because the injector nozzle is a certain distance from the combustion chamber, the mixing of gasoline and air is affected by the intake air flow and valve switch, and the tiny oil particles will be adsorbed on the pipe wall, which makes it difficult to achieve the theoretical air-fuel ratio, which is a problem that can not be solved by the traditional engine. To solve this problem, the fuel must be injected directly into the cylinder, which is what Audi's FSI direct fuel injection engine can do. The direct injection gasoline engine uses a similar fuel supply technology to that of a diesel engine, where a piston pump delivers the required pressure of 100 bar or more to supply gasoline to electromagnetic injectors located in the cylinder. The fuel is then injected directly into the combustion chamber at the optimum time by computer-controlled injectors. The internal shape of the combustion chamber is designed to create a strong swirl in the mixture, allowing the air and gasoline to mix well. Then the area around the spark plug can have a richer mixture, and the other surrounding areas have a thinner mixture, which ensures the thinnest possible combustion in the case of smooth ignition. This is the essence of stratified combustion. FSI technology utilizes two different fuel injection modes: stratified fuel injection and uniform fuel injection. The stratified mode is used when the engine is running at low or medium speeds, when the throttle is half-open and the air enters the cylinder through the intake tube and hits the top of the piston, which is shaped in a special way that creates the desired vortex near the spark plug. Toward the end of the compression process, a small amount of fuel is injected from the injector, creating a combustible gas. This stratified fueling method improves the economy of the engine to the fullest extent, because at lower speeds and lower loads, apart from the more concentrated oil/gas mixture that needs to be formed around the spark plug, the rest of the combustion chamber requires only a mixture with a high air content, which the FSI brings very close to the ideal condition. When the throttle is fully open and the engine is running at high speed, a large amount of air enters the cylinder at high speed to form a strong vortex and mix evenly with gasoline. This promotes the full combustion of fuel and improves the engine's power output. The computer constantly changes the fuel injection mode according to the working condition of the engine, and always maintains the most suitable fuel supply mode. The full utilization of fuel not only improves fuel utilization efficiency and engine output but also improves emissions. Since FSI direct injection engine has so many technical advantages, accordingly its requirements on engine hardware or oil must also be very high. First of all, its injectors are installed in the combustion chamber, gasoline is injected directly into the cylinder, the oil circuit must have a higher pressure than the cylinder in order to inject gasoline effectively into the cylinder. After the pressure in the fuel line is increased, the strength of the sealing of the joints of the pipe should also be increased. Thus, the design and manufacturing process of the injector also puts forward higher requirements. Moreover, since the injector is installed directly on the combustion chamber, it must have the ability to resist high temperature. Secondly, the compression ratio of the FSI direct injection engine is very high, reaching an astonishing 11.5, in which case the requirements for oil grade and oil quality are very strict. In terms of the current situation in China, high cleanliness gasoline of 98 must be used. As far as technology is concerned, the FSI direct injection engine is ideally suited to the needs of a market that is currently prone to rising fuel prices. As a trump card for Audi to fight with its competitors, this engine has its own strong vitality and will certainly lead the trend of engine development.

References:

Sina Motors and Autohaus